Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
Case	Tag   Price	Sales   Tax %	Raw Total   Incl. Sales Tax	Rounded   to Penny	Rounded   to Nickel	Rounded   to Dime
Purchase #1	$67.47	6.507%	$71.8603	$71.86	$71.85	$71.90
Purchase #2	$250.96	12.719%	$282.8796	$282.88	$282.90	$282.90
Purchase #3	$237.60	9.833%	$260.9632	$260.96	$260.95	$261.00
Purchase #4	$238.50	4.785%	$249.9122	$249.91	$249.90	$249.90
Purchase #5	$190.37	4.211%	$198.3865	$198.39	$198.40	$198.40
Purchase #6	$42.76	5.717%	$45.2046	$45.20	$45.20	$45.20
Purchase #7	$116.85	5.811%	$123.6402	$123.64	$123.65	$123.60
7 purchase totals =	$1,144.51		$1,232.8466	$1,232.84	$1,232.85	$1,232.90